I’m attempting to root some rose cuttings. I built an aerocloner and get good callusing on my cuttings, but they seem reluctant to put out roots.
Would an application of IBA or NAA rooting hormone powder on the cuttings at this point be beneficial in forcing roots?
I’m by no means in any position to give much advice about rooting cuttings - I’m definitely an amateur. But, I vaguely remember reading something about the optimal temperature being different for callous formation and root formation. I think callous formed better at a higher temperature.
As for rooting hormone…
I’ve been pampering a lemon cutting in a gallon Ziplock since December 20th. I’ve kept it around 75-80 degrees F, and I’m using half sand / half potting soil, just damp - not wet. I got great callous tissue to form within a week, on the bottom of the cutting and all along the inch-long scrapes. But no roots for several weeks after that even. So, I finally tried Rootone powder. The callous still didn’t form roots, but two roots sprouted out farther up the stem, above all the callous tissue. Go figure!
Anyway, good luck to you. Tom
In my experience, the callus may stay without evident roots for a long time–and roots may appear (as Tom noted) where there is no callus. What usually gets roots to emerge is the initiation of shoot growth. Since this takes place best at slightly higher temperatures than callus formation, maybe keeping the cuttings in a slightly higher temperature will help. Other things that seem to get a cutting in the mood for putting out roots: a good nitrogen level in the cutting, the right day length (maybe give the cuttings more hours of light), sufficient moisture, and enough of various hormones (which I won’t try to discuss here).
If you do a Google for (“root formation” “callus formation” rose), you’ll come up with a lot of reading matter. The Rhizopon people have several sites, including http://www.hortus.com , Hortus USA: 3rd Congress on Root Formation and the one below. Happy reading. If you find out the single most important factor, please report back to us.